The Lisburn councillor had been facing an internal disciplinary inquiry for "bringing the party into disrepute" after claiming she had been ordered by a DUP minister's special adviser to change her vote on maintenance contracts at a Housing Executive board meeting.

Last week, a Stormont inquiry found that the then Social Development Minister Nelson McCausland had acted inappropriately.

Rev Paisley, twin brother of North Antrim MP Ian, said DUP MLAs had acted as if "they are infallible" and could not admit that they were wrong about anything.

"There was never any honest intention on their part to face up to their wrongdoing, but every intention to humiliate someone who actually cares for the party's character and reputation," Rev Paisley wrote.

"There needs to be contrition - repentance in sackcloth and ashes - and there needs to be a purging of the leaven," he wrote.

"Until there is, the DUP's authority and credibility will continue to wane. If there's not a change of heart, and the action that goes with it, the party may die."

Writing in the Ulster Star, Mrs Palmer also warned that without strong leadership the DUP will "disintegrate".

"We believed the party would do what was right, but it didn't," she added.

While party leader Peter Robinson tweeted it was a "pity" some people could not be team players, Lagan Valley MP Jeffrey Donaldson paid tribute to the "valuable contribution" of Mrs Palmer.